The ability to conduct ions, and in particular Li+ -ions is the main function of the electrolyte in lithium-ion batteries. Within the lithium-ion-battery, the electrolyte belongs to the inactive materials, however, its effect on the chemical nature and morphology of the formed interphases at the electrode/electrolyte interfaces have a major influence on the cycle life, power capability and safety performance of the lithium-ion battery. Research on electrolytes for lithium-based batteries can be grouped into ceramic solid electrolytes, polymeric electrolytes, ionic liquid-based electrolytes, liquid organic electrolytes, liquid aqueous electrolytes, as well as hybrid electrolytes. However, most of the electrolytes used in commercial lithium-ion batteries are liquid organic solvent-based electrolytes, comprising a Li salt dissolved in a blend of aprotic organic solvents. Surprisingly, as compared to research outcome devoted to cathode cell chemistries, advances in electrolyte research and development have been scarce over the past 30 years.